Method for melting zinc dust



. v E. c. HANDWERK ETAL 2,457,553

METHOD FOR MELTING ZINC DUST Filed Dec. 21, 1945 2 Sheets-Shet 1 INVENTORS' 0 var r. xmnwwwr 6501M: TM/I/YLJEI? BY Mum? amurr.

ATTORNEYS Dec. 28, 1948. E. c. HANDWERK ETAL 2,457,553

METHOD FOR MELTING ZINC DUST Filed Dec. 21, 1945 2 Sheets-Sheet 2 INVENTORS 1? VIM-C. Ill/w wilrlr G'ORGE TMAII ER BY IIAHHY C. l/AUPT h I ATTORNEYS Patented Dec. 28, 1948 METHOD FOR MELTING ZINC DUST Erwin C. Handwerk, George T. Mahler, and Harry 0. Haupt, Palmerton, Pa., assignors to The New Jersey Zinc Company, New York, N. Y'., a corporation of New Jersey Application December 21, 1945, Serial No. 636,420

, 3 Claims.

divided metals such as metal powders, turnings, chips and the like, and more especially to the melting of zinc dust or blue powder. The object of the invention is to provide an improved method of melting zinc dust and other finely divided metals.

The melting of zinc dust and other finely di vided metals presents special difficulties because of the large surface areas characteristic of finely divided metal particles, and the frequent and indeed usual presence of oxide films on the surfaces of the particles. Moreover, finely divided metal particles tend to agglomerate and sometimes to sinter in the course of melting, and effective dispersion or breaking-up of these agglomerated or sintered particles requires special care and attention for satisfactory and complete melting. Furthermore, the surfaces of finely divided metal particles, particularly when filmed with oxide coatings, are difiicultly wet by the molten metal, and melting and coalescence of the particles is thereby retarded and sometimes even inhibited.

The present invention provides an effective and rapid method for melting zinc dust and other metal powders. In accordance with the invention, melting is carried out in a heated chamber having a bath or body of molten metal in the bottom thereof, and a shower of molten metal particles, derived from the bath, is produced in the chamber by hurling by centrifugal action a substantially continuous and upwardly-directed shower of the molten metal of such violence as to provide by itself and by its splashing against the confining upper portion of the chamber turbulent sheet-like showers of molten metal within the chamber. The particles of finely divided metal such as zinc to be melted are introduced into the shower of molten metal whereby they mingle and contact with the particles of molten metal and are thereby melted or entrapped in falling through the chamber. The molten metal shower is preferably produced by throwing into the chamber rapidly succeeding upwardly-directed sheets or showers of molten metal which splash against the walls and roof of the chamber and thereby produce a shower or rain of molten metal particles through which the finely divided metal to be melted passes from its point of delivery to the chamber. as fall on the molten metal are stirred into it by agitating the molten metal, preferably by the same agency that produces the molten metal shower.

The foregoing and other novel features of the Such solid metal particles 2 invention will be best understood from the following description taken in conjunction with the accompanying drawings, in which illustrate, by way of example, a melting apparatus in which the invention may advantageously be practiced, and in which Fig. 1 is a longitudinal sectional elevation of the melting apparatus,

Fig. 2 is a top plan of the apparatus, and

Fig. 3 is a transverse sectional elevation on the section line 33 of Fig. 1.

The apparatus as illustrated in the drawings comprises a generally elongated refractory furnace structure enclosing a chamber divided by a depending partition or baffle 5 into a heating zone or compartment A and a melting zone or compartment B. The chamber has a bottom or sole 6 supporting a bath or body of molten metal into which the partition 5 clips while permitting free communication of molten metal beneath the partitions lower edge. The compartment A is provided with an oil or gas burner l by which it is heated by reverberatory firing. The products of combustion escape through a stack 8', in the roof of the compartment A, provided with a suitable damper 9 for regulating the draft. The heating compartment A communicates, beneath the lower edge of its end wall l0, with a discharge well H having an overflow spout l2 determining the level (a) of the body of molten metal in the furnace chamber. The lower portion of the end wall ill dips into the molten metal between the heating compartment and the discharge well and seals the compartment from the atmosphere at this point. A collecting trough I3 receives the molten metal overflowing the spout l2 and conveys it to casting equipment or the like.

A feed hopper l4 having a gas-tight feeder i5 is mounted on the roof of the melting compartment B for introduoing'finely divided metal (e. g. zinc dust) into the compartment. A generally cylindrical rotor I6 is mounted transversely within the melting compartment B in such manner that it dips into the bath of molten metal. The rotor is positioned at one side of the delivery end of the feed hopper, and rotates in such a direction that the side of the rotor towards the delivery end moves downwardly so as to stir the finely divided metal into the molten metal. As viewed in Fig. 1, the direction of rotation of therotor is clockwise, as indicated by the arrow.

The rotor I6 is carried by a hollow or axiallybored metal shaft ll horizontally mounted in bearings l8 outside the furnace, structure. The

through its axial bore, the cooling medium being supplied to the bore at one endoftheshaft by a pipe 22 and discharged from the other end through a pipe 23.

The peripheral surface of the rotor I6 has a a plurality of circumferentially" spaced pockets-for cups 24. The shaft I1 is positioned ata level. substantially above that of the molten metal adapted to be held in the furnace chamber, and the rotor I6 is of such outside diameter that its lowermost pocket is beneath the molten metal level (a). The rotor is" rotated by" means of a pulley 25 secured to the-shaft IIfand' operatively connected to a suitable source of power; suchas an electricjmotor (not shown) The compartment B provided with. effective seals for preventing the leakage of molten metal through and the freezing of molten metal in the apertures in the side walls through which the shaft II extends. Thus; therotor IGhas'a later ally extending sleeve Z'IS at each end-thereofsurrounding the cement sleeVe'I9' where the latter extends through the wall of the compartment. The rotating sleeves 26 extend through stationary sleeves 21. Each stationary sleeve 2'! has a constricted portion 28', near its outer end, to provide a close clearance with the rotating sleeve 25, and is elsewhere spaced from the rotating sleeve to provide an elongated inner annular space 29; The outer ends of-the concentric sleeves I9, 26 and 21" are enclosed in a gas seal comprising a tight fitting cap or' housing 31 having: a gland bushing 32 through which the shaft II extends. A suitable non-oxidizing gas, such for example as carbon monoxide, ispumped' into the caps 3I through the inlet pipes 3-3 to maintain a s-ufliciently high gas pressure within the caps to prevent the entrance of air-between the stationary sleeves 21 and the rotating'sleevesifi. A vent-'31 is provided in the roof'of' the compartmentBfor the escape of the gas, which, if combustible, is burned at the discharge end of the vent. The temperature prevailing in the compartment B' is not sufiicient' to produce any vapor pressure of metal therein.

The sleeves Z'G-an'd 2 1 are so shaped'that molten metal does not accumulate in the elongated annular space 29* between the sleeves but, on the contrary; runs out by gravity into the molten metal at the bottom of the compartment. Thus, the ends of thestationary sleeves 21 extend into annular grooves 3'4 in the ends of the rotor IIi, and the lower portions oftheseends are internally beveled or thinned to form spouts 35- for dis-'- charging by gravity any molten metal" entering the-space 2'9: between the sleeves. The annular grooves 34 are outwardly flared to facilitate the flower-molten metal therefrom. The upper portion of the end of each. sleeve 21 is beveled or thickened to form a backwardly slopingspoutflfi" for guiding any molten metal falling on or'wet ting the upper surface-of'the: sleeve towards the compartment wall and thence; downwardly over theisleeveitor the body of 'molten metal. I

, by the flow of a cooling mediunnsuch'a's water;

Cooling of the shaft I1 permits the use of a metal shaft, and the sleeve I9 of insulating cement inhibits appreciable cooling of the melting compartment by the cooling medium flowing through the shaft, and eliminates any thermal stresses in the rotor IS. The special configuration. of"thestationary sl'eeveezli prevents-the collection and freezing of molten metal in the close clearance between the sleeves 26 and 27, and consequent stoppage of the drive shaft. The gas sea-ls prevent; the infiltration of air through the rotating contact between the sleeves 2S and 21,

and thus insure free-relative movement of these sleeves- In the practicei'ofthe invention in melting zinc d'ust'in the apparatus illustrated in the drawings, the zinc: dust is: continuously introduced into the melting compartment B throughthe hopper I4 and feeder I5. The rotor I5 is rotated at a relatively high speed, say around to R. P. M., clockwise as" viewed in Fig. 1 so that the'pockets 2 3 in rapid succession pick up-andthrow she'ets'or showers ofmolten zinc upwardly into'the compartment. The'p'ockets- 24 have agenerallyscooplike-section with a relatively long advancing flat sectionand a shallow semi-circular depression at the inner end or bottom of the pocket; The pockets terminate shortof thecircumferential peripheraTends of the rotor, so thatlittle or no molten zincis thrown laterally against the side wallsof the compartment. The upwardly directed an'd rapidly succeeding sheets or showers of moltenzinc splash into'the shower-or rainofmolten zinc particles falling through the compartment and also againstthe roof of the compartment, with the result that the compartment issubstantiallyfilled with sheet-like showers and moving particles of molten zinc which-form an ideal environment-for dissolving or entrapping soli'd 'particles of zinc dust and carryingithem to the molten" zinc bath, where they promptly melt; Additionally; the'position of therctor I-G" at one side of the delivery end' of the feed hopper with the side of the rotor approximate the falling particl'es of zinc dust-moving downwardly stirs the zinc'dust intothemoltenzinc. As a result of'this effective stirring of the zinc dust into-the-molten zinc and. the agitation of the molten metal by the rotor, the zinc dust is promptly and completely melted.

The heat required for melting is furnished by the reverberatory' firing of the compartment A by the-fuel burner I. This heatis readily trans mittedto the melting chamber through the par tition. or dividing wall.v 5: and through the: common body offmolten metal in the compartments A; and

B; Moltensmetakis;continuously withdrawn from the dischargezwell 1.1-, over the spout I2, at a rate substantially'equivalent to the rate at which zinc dust. is? introduced into themelting: compartment B, thusmaintaining a. uniform. V01l111'16r0f1 molten.

metal. in the. compartments AV and B;

The invention provides a highly efiicientmeth-- odof transforming zinc dust' tosmolten zinc. If not too heavily oxidized, the" zinc dust can be completely melted down to molten metal without aflux. If heavily oxidized; a salammoniac or equivalent flux maybe desirable. In addition to zinc dust, theinvention is applicableto the melt; ing of othermetal' powders-turnings, chips etc.

We claim:

1'. The method of melting finely divided zinc in a heated melting chamberhaving abody of molten zinc in the bottom thereof which--comprises hurling by centrifuga-l action a substantiall'y continuous and upwardly-directed shower of said molten zinc of such violence as to provide by itself and by its splashing against the confining upper portion of the chamber turbulent sheet-like showers of molten zinc within the chamber, and introducing the finely divided zinc into said shower of molten zinc whereby the particles of zinc to be melted mingle and contact with the molten zinc thrown upwardly into the chamber and are melted or entrapped thereby.

2. The method of melting finely divided zinc in a heated melting chamber having a body of molten zinc in the bottom thereof which comprises hurling by centrifugal action a substantially continuous and upwardly-directed shower of said molten zinc of such violence as to provide by itself and by its splashing against the confining upper portion of the chamber turbulent sheet-like showers of molten zinc within the chamber, introducing the finely divided zinc into said shower of molten zinc whereby the particles of zinc to be melted mingle and contact with the molten zinc thrown upwardly into the chamber and are melted or entrapped thereby, continuously withdrawing molten zinc from said chamber into a communicating enclosed chamber at a rate substantially equivalent to the rate at which finely divided zinc is introduced by maintaining a substantially uniform volume of molten zinc in the bottom of said communicating chamber, and supplying to said communicating chamber the heat required for maintaining the body of zinc in molten condition.

3. The method of melting finely divided zinc in a heated melting chamber having a body of molten Zinc in the bottom thereof which comprises picking up in rapid succession from said body of molten zinc small amounts thereof and hurling by centrifugal action said small amounts of molten zinc upwardly in the melting chamber and against the walls thereof and thereby providing sheet-like showers of molten zinc within the chamber, and introducing the finely divided zinc into said shower of molten zinc whereby the particles of zinc to be melted mingle and contact with the molten zinc thrown upwardly into the chamber and are melted or entrapped therey.

ERWIN C. HANDWERK. GEORGE T. MAHLER. HARRY C. HAUPT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Sweden May 24, 1922 Number Number 

